JP2000322021A - Brightness control device for planar display device and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the area of chips and to change the brightness of a desired portion by inputting a scan signal additionally driving part of a scanning line and an image data signal in a margin scanning time, and displaying them on a panel. SOLUTION: This brightness control device is provided with a reference signal section 10 receiving an external image signal and outputting a scan signal of the prescribed duty ratio and a display image data signal, a controller 20 changing the duty ratio and generating a margin scanning time, and a display section 30 receiving the changed duty ratio and image data and displaying them on a panel. The data drive circuit 32 of the display section 30 applies the output data of a memory section 13 to data lines, and a scan drive circuit 31 applies the drive signal from a control circuit section 12 to a scanning line and displays data together with the drive signal. The controller 20 allocates the margin scanning time generated at the changed duty ratio to additionally drive a specific line while maintaining the drive signal of the predetermined duty ratio at the same frame frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat display device, and more particularly, to a device for controlling brightness of a flat display device by changing a duty ratio without consuming extra power and adjusting a display time. And methods. Note that the duty ratio means a ratio of driving one scan line to one frame time.

At present, various display devices such as a CRT (Cathode Ray Tube) are used in various fields from a small pocket-sized television to a large screen. With the development of electronic technology, miniaturization, weight reduction, and low voltage have been pursued, and a new flat display device having characteristics of being thin, light, and low in power consumption has been developed.

[0003] As the flat display device of this new form, an LCD (Liquid Crystal Display), a PDP (Pla
sma Display Panel), VFD (Visual Fluorescent Disp.
aly) and FED (Field Emissio
n Display), LED (Light Emitting Diode), EL (Ele
ctroluminescence), etc.

Hereinafter, a driving circuit of a conventional flat panel display device will be described with reference to the accompanying drawings. FIG. 1 shows a drive circuit diagram of a flat display device according to the prior art, and a system interface unit for converting a control signal or data input from the outside into data or a control signal necessary for display of the display device. 1 and
A memory unit 3 storing data and control signals converted by the system interface unit 1; a data drive circuit 4 for applying output data of the memory unit 3 to a large number of data lines; Control circuit unit 2 that determines a constant duty ratio by a control signal
And a scan drive circuit 5 for applying a drive signal with a duty ratio determined by the control circuit unit 2 to a number of scan lines.

The scan line and the data line cross each other, and a portion where the scan line and the data line cross each other, that is, a pixel is selectively made to emit light. Images and characters are displayed by the light emission of the selected pixels.

FIG. 2 shows a driving timing diagram of a conventional flat display device and a flat display device displayed by the driving timing diagram. Referring to FIG. 2, when a specific scan line is selectively driven, a data line is also selectively driven, and a pixel at which the scan line and the data line intersect is selectively turned on / off.
"G" is displayed.

That is, when a first scan line is driven and turned on, a data line necessary for displaying data among a large number of data lines is turned on before it is turned off, so that a desired position of the scan line can be obtained. Can display the data.

In such a method, the brightness of a displayed pixel is proportional to the time during which each scan line and data line are on. The time during which the scan line is turned on varies depending on the size of the duty ratio being turned on and the time of one frame.

That is, as shown in FIG.
Assuming that the time of one frame is T _F , the time during which each scan line is being driven, that is, the duration of the drive pulse is T
_F / 40. Then, as shown in FIG. 2, when all the ON times of the data lines are driven to be the same, all the pixels of the panel have the same brightness.

Also, in order to efficiently search data in an icon line or data search of a portable terminal, when a specific portion of the display panel is to be displayed brighter than other portions, the desired data line is set to a high level. A method of applying a voltage or a high current has been used. Another method uses a method of adjusting the on-time of the data line.

FIGS. 4A and 4B are data drive circuit diagrams of a conventional flat display device, wherein FIG. 4A is a circuit diagram of a current drive type, and FIG. 4B is a circuit diagram of a voltage drive type.
As shown in FIGS. 4A and 4B, a data line to be displayed brighter than a certain data line is switched by switching and connected to a high voltage source or a high current source. As a result, the high voltage or high current is applied to the specific data line to be displayed brighter than the other data lines via the data drive 6, and the specific line on the display panel 7 is displayed brighter.

However, the above-described brightness control method of a flat display device according to the related art requires an additional circuit to apply a high voltage or a high current to each data line, and requires a chip. The area increases. In addition, in the case of the voltage drive type, a stable voltage must always be maintained, and in the case of the current drive type, there is a problem that the current matching problem of each current source must be considered.

Further, in the method of adjusting the on-time of each data line, since a PWM (Pulse Width Modulation) control circuit must be installed in each data line, there is a problem that the chip area increases.

[0014]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above problems,
Minimizing chip area by eliminating additional circuit elements,
It is an object of the present invention to provide a brightness control device and a brightness control method capable of appropriately changing the brightness of a desired portion using only digital signals without extra power consumption.

[0015]

According to the present invention, there is provided a brightness control apparatus for a flat display device, which receives an external video signal to display a scan signal having a predetermined duty ratio. A reference signal section that outputs a video data signal to be output, a control section that changes a duty ratio output from the reference signal section to generate a marginal scan time, and a duty ratio changed by the control section and the video data. And a display unit for displaying on a panel.

Another feature of the present invention is that the control unit generates a number of clocks necessary for changing the duty ratio, and a frequency selection unit that selects one of the generated clocks as a reference clock. Unit, a duty ratio control unit that sets a duty ratio with a selected reference clock to control a marginal scan time, a scan signal control unit that generates a signal for scan line driving with the set duty ratio, When allocating extra scan time to a specific scan line and driving the allocated line, a data signal control unit that changes data using masking, and a display control that synchronizes the duty ratio control unit and the scan signal control unit And parts.

Still another feature of the present invention is that the control unit changes a scan time for driving a scan line during one frame time by changing a duty ratio, and adds a margin scan time to a scan line to be displayed brightly. And a data control unit that drives all or part of the data for the additionally driven scan line and performs masking on the remaining data.

According to another aspect of the present invention, there is provided a brightness control method for a flat panel display device, comprising: generating a margin scan time by adjusting a duty ratio of a scan time while maintaining the same one frame frequency. Allocating the generated extra scan time to each scan line to be displayed brightly, and driving the scan line; displaying only the drive data of many data lines to be displayed brightly; masking the data of the remaining data lines. And selectively driving the data lines.

Another feature of the present invention is that the brightness of a specific data line is adjusted by masking the data of the data line displayed brighter than the other data lines and the spare scan time of the scan line.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a brightness control device for a flat display device according to the present invention will be described below with reference to the accompanying drawings. FIG. 5 is a driving circuit diagram of the flat panel display device according to the present invention. The reference signal unit 10 receives an external video signal and outputs a scan signal having a predetermined duty ratio and a video data signal to be displayed. , A control unit 20 that changes the duty ratio output from the reference signal unit 10 and generates a marginal scan time
And a display unit 30 for inputting the duty ratio and the video data changed by the control unit 20 and displaying them on the panel.

The reference signal unit 10 converts a control signal or data input from the outside into a control signal necessary for display on a panel. The system interface unit 11 performs a duty cycle according to the control signal converted by the system interface unit 11. It comprises a control circuit section 12 for determining the ratio and a memory section 13 for storing data corresponding to the control signal converted by the system interface section 11.

The display section 30 includes a data drive circuit 32 for applying output data of the memory section 13 to each data line.
And a scan drive circuit 31 that applies a drive signal from the control circuit section 12 to a scan line to display data together with a signal from the data drive circuit 32. The control unit 20 changes the duty ratio of the drive signal having the duty ratio determined by the control circuit unit 12 while maintaining the same frame frequency, generates a margin scan time, and adds the specific line to a specific line. Allocate to drive to.
The allocation method will be described later.

FIG. 6 is a block diagram of the control unit 20 according to the present invention. The control unit 20 receives the main clock output from the control circuit unit 12 and generates a number of clocks necessary for changing the duty ratio.
And a frequency selector 22 for selecting one of a number of generated clocks as a reference clock, and a duty ratio controller 2 for setting a duty ratio with the selected reference clock.
4, a scan signal control unit 25 that generates a signal for scan line driving at a set duty ratio, and a display control unit 23 that synchronizes the duty ratio control unit 24 with the scan signal control unit 25. I have. Frequency selector 2
The duty ratio can be arbitrarily adjusted according to the frequency selected in Step 2. Further, a data signal control unit 26 for masking a data signal as necessary is provided.

The control unit 20 configured as described above changes the duty ratio while maintaining the same frame frequency,
By driving each scan line and allocating the remaining scan line drive time (margin scan time) to a specific line and driving it additionally, the specific scan line is displayed brighter than the other scan lines. .

[0025] In order to vary the duty ratio while maintaining the same frame frequency must be to convert the frequency required for timing control, expressed in the frequency necessary control clock this time, the control clock f _Contorl is Calculate as follows: f _control = (number of clocks required to display one scan line) * (number of frames) * (duty ratio) ^{-1 As} an embodiment, as shown in FIG. Is 1/40, if 100 clocks are required to display one scan line of data, the control clock f ₄₀ is 280
kHz. f ₄₀ = 100 * 40 * 70 = 280 kHz However, the duty ratio is set to 1 under the same conditions as in this embodiment.
When it is changed to / 48, the control clock f ₄₈ becomes f ₄₈ = 100 * 48 * 70 = 336 kHz as follows.

In FIG. 6, the frequency conversion unit 21 generates a clock corresponding to the conversion of the duty ratio by the method described above. When the duty ratio is set, the clock generated by the frequency converter 21 is selected as a control clock by the frequency selector 22 and used as a reference clock for the entire timing circuit. As described above, in the control signal input through the system interface unit 11, the number of pulses that can drive the scan line during one frame time changes according to the set duty ratio.

FIG. 7 shows that the duty ratio according to the present invention is 1/4.
8 is a scan line drive timing diagram set to 8;
8 drives 40 scan lines in FIG. 7 and remains
The scan time will re-drive a particular scan line.
FIG. 6 is a timing chart allocated and added as follows. As shown in FIG.
If the duty ratio is changed to 1/48,
Time T _FAssigns to each scan line
Scan time is T_F/ 48, 40 scans
Scan line remaining scan time (extra time,
T_R) Is 8T_F/ 48. That is, 8 scan lines
Can be driven again. I
Therefore, this extra time is referred to as extra scan time.

As shown in FIG. 8, when a surplus time (T _R ) is divided by one pulse for each of the scan lines 1 to 8 and a pulse signal is applied, scan driving of the added scan lines 1 to 8 is performed. Time is T _F / 4
8, ie, twice as large as the other scan lines. Therefore, the scan line to which the surplus time is assigned has twice the drive time as compared to the other scan lines.

The method of additionally applying a pulse signal is roughly divided into three methods. First, a method of sequentially displaying the respective scan lines from the beginning, and drives by adding some or all of the excess time to the scan lines to be displayed brighter than the other scan lines (T _R).

Second, there is a method of allocating a part or all of the surplus time (T _R ) to scan lines for displaying brighter than the other scan lines, driving first, and then sequentially displaying the lines.

Third, there is a method of changing the brightness of a specific line in a stepwise manner.
_R ) is adjusted so that the brightness of a scan line displayed more brightly than other scan lines is changed stepwise.

FIG. 9 shows the invention of the first method, in which four out of the eight pulses of the surplus time (T _R ) are assigned to the first line.
The remaining four were applied to the second line. In such a case, the driving time of the first and second scan lines is 5T _F / 48
, And it is 5 times larger than T _F / 48 of the remaining lines, so that the first and second lines look brighter than the other lines.

FIG. 10 shows the invention of the second method.
The surplus time (T _R) 8 pulses
After adding everything continuously, drive the remaining lines sequentially
I do. Therefore, the first line is 8 times the other lines
Looks bright.

FIG. 11 shows the third method of the present invention, in which the surplus time (T _R ) is masked to change the brightness of a specific line step by step for each frame, so that the scan line has a desired brightness. Adjust. The masking time (T _M ) is generated by the scan signal control unit 35 in a continuous combination.

FIG. 12 is a view showing a flat display apparatus in which surplus time is allocated to scan lines 1 to 8 and an additional pulse is applied to display the scan lines 1 to 8 in the manner described above. Therefore, the present invention can display the emphasized character “LG” brighter than “HB”. However, the method shown in FIG. 12 is controlled for each scan line, and is not suitable for displaying only a part of the data line brightly. That is, if only “L” is to be displayed brightly in the “LG” data displayed brightly in FIG. 12, it is impossible to realize it because it is displayed in units of scan lines. Thus, in order to emphasize the data of some data lines, not only the scan lines but also the data lines should be controlled.

Therefore, it is desirable to use a masking method as a method for controlling the data lines. As shown in FIG. 8, when a specific scan line is additionally driven, data of a data line which is to be displayed brightly among many data lines is masked, and data of the remaining data lines is masked. Then, the display may be prevented from being displayed brightly.

Therefore, the control unit 20 further includes a data signal control unit 26 for masking a data line when a pulse is applied to a specific scan line during the spare scan time. The data signal controller 26 selectively turns on / off the data displayed on the selected scan line and masks a portion of the data when applying additional pulses to a particular scan line during the extra scan time. Emphasize certain parts.

Accordingly, in the first method, when the entire scan lines 1 to 40 are first scanned, the data signal control unit 26 performs the same operation as that of driving a general flat display device, and thereafter increases the brightness. When an additional pulse is applied to specific scan lines 41 to 48 to be displayed, the data can be partially displayed bright by masking while leaving only the data of the portion to be displayed bright.

FIG. 13 is a configuration diagram displayed by using data masking according to the present invention, and FIG. 14 is a timing chart showing waveforms for driving the operation of FIG.

Referring to FIG. 14, one frame time (T _F )
During the normal scan time, each pixel has the same drive time, resulting in the same brightness. Then, while driving the scan lines 1 to 8 to be brightened during the remainder scan time (T _R ), only 1 to 6 out of a large number of data lines are driven. Character has twice the drive time as compared to other characters. Therefore, as shown in FIG. 10, only the character "L" on the data lines 1 to 6 out of the characters on the 12 data lines is displayed brighter than other characters.

In addition, the drive time of the scan lines to be driven extra can be changed stepwise, and it is also possible to additionally drive a desired number of scan lines. In the case of data lines, the masking time (T _M ) can be changed stepwise, and all the data of a desired large number of data lines can be masked.

As described above, the scan control unit 21
The surplus time (T _R)
By assigning them to appropriate scan lines,
Adjust the brightness of the desired scan line, and
Only the data of the data line whose brightness is desired by the control unit 22
By selectively controlling and adjusting the brightness, the display
You can adjust the brightness of the desired position on the screen
Wear.

At this time, as the duty ratio increases, the drive time of each scan line decreases. However, the drive time of each scan line by adjusting the duty ratio decreases in the same manner as a whole, and the decrease time is the normal drive time. Therefore, the size does not greatly affect the overall data display, for example, 1/40 to 1/40.

The contents described above are the contents of the embodiments, and it will be obvious to those skilled in the art that various changes and modifications can be made without departing from the technical idea of the present invention. Therefore, the technical scope of the present invention is not limited to the contents described in the invention, but should be limited by the claims. In particular, each number given as an example is merely an example, and it goes without saying that it can be changed as appropriate.

[0045]

According to the brightness control apparatus and method for a flat display device according to the present invention as described above, when displaying data on the display device, there is no extra power consumption and the chip area is not increased so much. The brightness of a specific line can be arbitrarily changed and displayed.

When displaying data on the display device,
Of the data displayed on the specific line or panel, the brightness of the data at the specific position may be changed stepwise and displayed.

Further, when applied to various flat display devices such as portable terminals, there is an effect that data of a specific portion can be displayed more clearly without extra power consumption.

Furthermore, since the brightness of the data at a specific position is adjusted without using an additional circuit inside the chip and can be realized only by a digital circuit, there is a great advantage in utilizing the chip area.

[Brief description of the drawings]

FIG. 1 is a drive circuit diagram of a flat display device according to a conventional technique.

FIG. 2 is a driving timing diagram of a flat display device according to the related art and a drawing showing the flat display device displayed thereby.

FIG. 3 is a scan line drive timing diagram according to the related art in which a duty ratio is set to 1/40.

FIG. 4 is a circuit diagram (a) of a current drive type and a circuit diagram of a voltage drive type (b) of a flat display device according to a conventional technique.

FIG. 5 is a driving circuit diagram of the flat display device according to the embodiment of the present invention.

FIG. 6 is a block diagram of a control unit according to the embodiment of the present invention.

FIG. 7 shows a duty ratio of 1/4 according to the embodiment of the present invention.
FIG. 9 is a scan line drive timing diagram set to 8;

8 is a timing chart in which 40 scan lines are driven in FIG. 7 and the remaining scan time is additionally applied to an arbitrary scan line.

FIG. 9 is an invention based on scan line driving according to the embodiment of the present invention.

FIG. 10 is another embodiment of the present invention.

FIG. 11 is still another embodiment according to the present invention.

FIG. 12 is a view showing a flat display device applied to margin scan lines 1 to 8 and displayed according to an embodiment of the present invention;

FIG. 13 is a configuration diagram displayed using data masking according to the embodiment of the present invention.

FIG. 14 is a timing chart showing waveforms for driving the operation of FIG. 13;

[Explanation of symbols]

 1, 11: System interface unit 2, 12: Control circuit unit 3, 13: Memory unit 4, 6, 32: Data drive circuit 5, 31: Scan drive circuit 7: Display channel 10: Reference signal unit 20: Control unit 21 : Frequency conversion unit 22: Frequency selection unit 23: Display control unit 24: Duty ratio control unit 25: Scan signal control unit 26: Data signal control unit 30: Display unit

Claims (12)

[Claims] 1. A scan signal having a specific duty ratio, which is a signal for driving a scan line by inputting an external video signal, and a video data signal for driving a data line according to contents to be displayed. A reference signal unit to be output; a control unit that changes a duty ratio of a scan signal output from the reference signal unit to generate a marginal scan time; and drives all scan lines with the duty ratio changed by the control unit. And a display unit for inputting the image data signal and displaying the image data signal on a panel by additionally driving a scan line during a spare scan time. apparatus. 2. The control unit includes: a frequency conversion unit that generates a number of clocks necessary to change a duty ratio; a frequency selection unit that selects one of the generated clocks as a reference clock; A duty ratio control unit that determines a duty ratio based on the selected reference clock; a scan signal control unit that generates a signal for driving a scan line at the determined duty ratio; and the duty ratio control unit and a scan signal control unit. 2. A display control unit for synchronizing.
4. The brightness control device for a flat display device according to claim 1. 3. The plane according to claim 2, wherein the control unit further includes a data signal control unit that converts data using masking when driving a specific scan line with a marginal scan time. Display device brightness control device. 4. The system according to claim 1, wherein the reference signal unit is configured to convert a control signal or data input from the outside into a control signal required for display on a panel, and a control signal converted by the system interface unit. The brightness control of a flat display device according to claim 1, further comprising: a control circuit for determining a duty ratio; and a memory for storing data according to the control signal converted by the system interface. apparatus. 5. The control unit changes a duty ratio to change a scan time during which a scan line can be driven during one frame time to generate a margin scan time, and generates a margin scan time for a scan line to be displayed brightly. 2. The scan control unit according to claim 1, further comprising: a scan control unit for allocating the data, and a data control unit for driving all or a part of the data for the scan line to which the extra scan time is allocated, and performing the masking for the remaining data. A brightness control device for a flat display device according to any one of the preceding claims. 6. A data drive circuit for applying output data of the control unit to each data line, and a scan drive circuit for applying a drive signal from the scan control unit to a scan line for display. The brightness controller of claim 1, wherein the brightness controller comprises: 7. A first step of generating a margin scan time by adjusting a duty ratio of a scan time while maintaining the same frame frequency, and additionally to each scan line for displaying the generated margin scan time brightly. Allocating and driving the scan lines in a second step. 8. The method of claim 2, further comprising the step of displaying only driving data of a plurality of data lines to be displayed brightly, masking data of the remaining data lines, and selectively driving the data lines. The brightness control method for a flat display device according to claim 7, wherein: 9. The method of driving a data line further comprises adjusting a data brightness by adjusting a data driving time of a specific data line to be displayed bright through partial masking. The brightness control method of a flat display device according to claim 8, wherein: 10. The method of driving the scan lines includes: sequentially driving each scan line from the beginning using a fixed duty ratio; and providing a scan line that is to be displayed brighter than an arbitrary scan line. The method of claim 7, further comprising: allocating a part or all of the scan time and driving the scan time. 11. The step of driving the scan line includes: selectively allocating a part or all of a marginal scan time to a scan line that is displayed brighter than an arbitrary scan line first, and driving the scan line. The method according to claim 7, further comprising: sequentially driving all scan lines using a constant duty ratio. 12. The method of driving a scan line, comprising: adjusting brightness by adjusting a driving time of data of a specific scan line to be displayed brighter than an arbitrary scan line through partial masking. The method of claim 7, further comprising: controlling the brightness of the flat display device.